Impact fuzes for spinning explosive projectiles and more particularly basedetonatingfuzes of the type equipped with a mechanical auto-destruction device



Sept. 6, 1966 w. GUERNE IMPACT FUZES FOR SPINNING EXPLOSIVE PROJECTILESAND MORE PARTICULARLY BASE-DETONATING FUZES OF THE TYPE EQUIPPED WITH AMECHANICAL AUTO-DESTRUCTION DEVICE Filed Feb. 18, 1964 2 SheetsSheet lSept. 6, 1966 w. GUERNE 3,270,670

IMP C FUZES FOR SPINNING EXPLOSIVE PROJECTILES AND MORE FA CULARLYBASE-DETONATING FUZES OF E TYPE EQUIPPED WITH A MECHANICAL AUTO-DESTRUCN DEVICE Filed Feb. 18, 1964 2 Sheets-Sheet 2 1? L IQT United StatesPatent This invention relates to those impact fuzes for explosiveprojectiles spinning about their longitudinal axis particularlysmall-caliber projectiles (of the order of 20 to 50 mm.) foranti-aircraft or aircraft-mounted automatic weapons-which are equippedwith a mechanical auto-destruction device comprising, in addition toother components, centrifugal locking means which are maintained in alocking position so long as the rotational speed of the projectile aboutits axis remains above a predetermined value, said locking meanstemporarily restraining an intermediate member in an inoperativeposition, which member is adapted when released and in response toelastic means to trip the fuze, usually by the plunging movement of afiring pin. The invention is more particularly though not exclusivelyapplicable to so-called base-detonating fuzes, which are designed to befitted to the base end of explosive projectiles.

It is the chief object of the present invention to provide an improvedimpact fuze of the above-mentioned type that is notably characterized byits attenuated sensitivity.

The present invention relates to an impact fuze of this type comprisinga mechanical auto-destruction device having a first rearwardly directedsurface against which bear the centrifugal locking means of saidauto-destruction device so long as the rotational speed of theprojectile remains above a predetermined value, below which elasticmeans controlling a centrifugal-lockingmeans-supporting intenmediatemember become preponderant and cause percussion of the fuze by alongitudinal forward movement of said intermediate member, characterizedin that there is provided, along the axipetal paths which saidcentrifugal locking means are constrained to follow in their housings inorder to escape from said first surface, a second forwardly directedsurface supported by a longitudinally movable weight which is free tomove rearwardly relative to said centrifugal-locking-means-supportingintermediate member in response to the pressure exerted on said secondsurface by said centrifugal locking means as the same follow theiraxipetal escape path, the movement along this path being thus restrainedin the event of an impact since said centrifugal locking means are thenconstrained to overcome the forwardly directed inertia force of saidweight in order to escape from said first surface, and it will thereforebe manifest that this restraining effect has an attenuating influence onthe sensitivity of the fuze.

The description which follows with reference to the accompanyingnon-limitative exemplary drawings will give a clear understanding of howthe invention can be carried into practice.

Referring to the drawings filed herewith:

FIGURE 1 shows in side elevation, in fragmental longitudinal section andwith cutaway portions, a base-detonating fuze with mechanicalauto-destruction device for fitting to a spinning explosive projectile,as executed in ac cordance with the invention, the component partsthereof being shown in the inoperative or safe configuration, and

FIGURES 2 to 4 show the basic components of the auto-destruction deviceof said fuze in the positions they occupy when the round is firedsubsequent to arming of the fuze, and subsequent to an impact ofsufiicient force to trip the fuze, respectively.

Referring to the accompanying drawings, there is shown thereon abase-detonating fuze with mechanical autodestruction device for asmall-caliber spinning explosive projectile of up to 30 mm., say, and itwill of course be understood that the fuze as a whole, with theexception of the mechanical auto-destruction device, may be devised inany convenient manner provide-d that it comprises an intermediatemember, hereinafter assumed to be a firing pin adapted to belongitudinally slidable forwardly whereby to detonate the priming chargeof the fuze.

Referring first to FIGURE 1, there is shown thereon a base-detonatingfuze case 1 having therein an axial bore 2 into which is fitted a socket3 comprising a transverse wall 3a embodying a central cylindrical holefor slidably receiving therein a forwardly pointing firing pin 4, saidfiring pin being urged forwardly by a spring 5 bearing against the rearend closure of said fuze case and being adapted to coact, in the eventof an impact or autodestruction, with a primer (not shown) positionedahead of said transverse wall 3a. In order to restrain the firing pin 4in its retracted position until the round is fired (fuze in safeconfiguration), provision is made for centrifugally releasable lockingmeans comprising two half-rings 6 inseited between the wall 3a and aflange 4a provided at the rear of firing pin 4, said half-rings beingsurrounded by a spiral strip 7 and a split sleeve 8 which spreads apartunder the effect of centrifugal force and thereby enable half-rings 6 tospread apart in turn whereby to release said firing pin 4 (fuze armed).

Referring still to FIGURE 1, the mechanical autodestruction devicecomprises, in the manner well known per se, in addition to the firingpin spring '5 referred to, centrifugal locking means consisting of balls9 disposed within radial housings embodied in the flange 4a of firingpin 4. In response to centrifugal force, said balls 9 bear against afirst rearwardly directed frusto-conical surface 10 which is positionedsubstantially level with said flange when the firing pin is locked inits retracted position (fuze in safe configurationsee FIGURE 1)..

Before proceeding with a description of the principal feature of thepresent invention, it is thought necessary, for a proper appreciation ofthis specific feature and of the advantages stemming therefrom, toexplain forthwith the manner of operation of the assembly hereinbeforedescribe-d, firstly after the round is fired, secondly in the event ofan impact, and thirdly in the event of operation of the auto-destructiondevice (if no impact occurs).

Immediately upon emerging from the gun barrel, and in response to thecentrifugal force engendered by the spin imparted to the projectile, theballs 9 are pressed firmly against the surface 10, thereby temporarilypreventing any forward motion of the firing pin 4. This centrifugalforce in addition causes spreading open of split sleeve 8, loosening ofspiral strip 7 and spreading open of half-rings 6, thereby releasing thefiring pin 4 which, though urged forwardly by spring 5, is restrained inits retracted position by balls 9.

The fuze is then ready to trip in the event of an impact occurring,which tripping takes place when the forwardly exerted inertia forces setup, at the instant of impact, in the movable compound comprising firingpin 4 and balls 9 are sufiicient to overcome the restraining forceexerted by said balls.

If no impact occurs, automatic destruction of the projectile will takeplace when the centrifugal force acting upon the balls 9 is no longersufficient to offset the urge exerted by spring 5. Said spring 5 willthen first constrain the balls 9 to retract into their radial housingsand subsequently constrain the consequently released firing pin 4 tomove forwardly and strike the fuze priming charge, whereby to causeauto-destruction of the projectile.

As a result of the functional arrangement described hereinabove, thesensitivity of the fuze to impact is all the greater as the mass of themovable compound comprising firing pin 4 and balls 9 is greater; for,all other things being equal, the inertia forces which urge said movablecompound forwardly and which must overcome the restraining force exertedby the locking balls 9 are proportional to the mass of said movablecompound.

In some instances, however, it may be preferable to attenuate thesensitivity of a fuze of this type in order to preclude its trippingwhen the projectile passes through comparatively thin, low-resistanceobstacles and thereby ensure that it remains armed and ready to betripped by a subsequent more violent impact.

It might well be thought that such attenuation could readily be achievedby merely lightening the firing pin 4. Although theoretically sound,this solution is in fact impracticable, due to the fact that the firingpin must posses adequate mechanical strength to withstand the shockloadings it sustains when the projectile is fired, which in turnprohibits any substantial lightening of the firing pin for a given typeof fuze.

The principal feature of the present invention provides a ready solutionto the problem referred to precedingly, to wit that of attenuating thesensitivity of a basedetonating fuze with sliding firing pin andball-type autodestruction device as hereinbefore described, withoutentailing any modification of the basic fuze components and, above all,without lightening the firing pin or modifying the auto-destructiondevice thereof.

Provision is accordingly made, along the axipetal paths followed by theballs 9 in their housings, for a second forwardly directed surface 11provided on a weight 12 mounted in a bore provided therefore in theflange 4 whereby to be axially movable rearwardly relative to firing pin4, when the same moves forwardly, and, by reason of a small axialclearance provided between said balls 9 and said second surface 11,initially also when the weight 12 bears against the end closure of itshousing.

Thus, when an impact occurs, the balls 9 are urged forwardly by firingpin 4 under the effect of its inertia; however, in order to escape fromthe first surface 10 on reaching the end of their axipetal movement,said balls must thrust the weight 12 rearwardly of the firing pin, andthis must be done against the countering inertia force of the weight 12which applies the second surface 11 against the balls 9 and therebyrestrains their axipetal movement.

Thus, all other things being equal, the presence of the weight 12 willattenuate the sensitivity of the fuze and most significantly, this willhave been achieved Without the need to dangerously lower the mechanicalstrength of its firing pin and without affecting its auto-destructioncharacteristics, in respect of which the additional weight will havevirtually no effect.

All other things being equal, the weight 12 can be rendered moreeffective by constituting it from a material such as brass of a densitygreater than that of the material used for the firing pin 4 (lightalloy, for example).

It will readily be appreciated from the foregoing that the sensitivityof the fuze can be effectively adjusted in the assembly stage byoperating in particular on the mass of the additional weight 12 andpossibly also on the slope of the surface 11. It will also be seen thata basedetonating fuze devised as hereinbefore disclosed has itssensitivity attenuated without affecting the resistance to motion of thefiring pin itself.

Reference is next had to FIGURES 1 to 4 for a detailed explanation ofthe relative positions of the moving parts of the fuze at certainspecific moments of the fuze operation.

In its inoperative position, the firing pin 4 is locked as shown inFIGURE 1.

When the round is fired, said firing pin is thrust by inertia intopressure contact against the weight 12, which weight is in turn thrustinto pressure contact against the end closure of its housing, while theballs 9 are urged outwardly (position shown in FIGURE 2).

At this stage, the firing pin is released and, due to the decelerationof the projectile, the weight 12 lifts slightly off the end closure ofits housing and applies its surface 11 against the balls 9, which ballsare clamped, as it were, between the surfaces 10 and 11 (position shownin FIG- URE 3).

In the event of an impact of force greater than the sensitivitythreshold of the fuze, the firing pin urges the balls 9 forwardly, whichballs, having thrust the weight 12 rearwardly, leave the surface 10,whereupon no further substantial force subsists to counter thepercussion stroke of the firing pin 4 (position shown in FIG- URE 4).

In a general manner, while the above description discloses what isdeemed to be a practical and efficient embodiment of the presentinvention, said invention is not limited thereto as there might bechanges made in the arrangement, disposition and form of the partswithout departing from the principle of the invention as comprehendedwithin the scope of the appended claims.

What I claim is:

1. An impact fuze for a spinning propectile which comprises, incombination, a fuze case fixed with respect to said propectile andhaving a longitudinal axis of rotation, a firing pin slidablelongitudinally in said case in the direction corresponding to firing inresponse to the stopping of said projectile by an obstacle, spring meansin said fuze case operatively connected with said firing pin for urgingit longitudinally with respect to said case in said direction, lockingmeans for yieldingly preventing said firing pin from moving in saiddirection as long as the speed of revolution of said projectile is abovea given value, said locking means comprising, on the one hand, a surfaceof said fuze case of revolution about said axis, said surface havinggeneratrices oblique to said axis and converging in said direction, and,on the other hand, adapted to cooperate with said surface by slidingengagement therewith, rounded centrifugal members guided in said firingpin radically and transversely to said axis, whereby an inward movementof said centrifugal members toward the axis of said fuze case takesplace when the speed of revolution of said fuze case about said axisdrops below said given value, and an inertia part slidablelongitudinally in said firing pin and having a surface thereof, ofrevolution about said axis and converging in the same direction as saidfirst mentioned surface, in engagement with said centrifugal members,whereby said inertia part is pushed longitudinally in a directionopposed to the first mentioned direction with respect to said fuze casein response to a movement of said centrifugal members toward said axis.

2. An impact fuze according to claim 1, wherein said centrifugal membersare balls.

3. An impact fuze according to claim 1 wherein said firing pin isprovided with a longitudinal bore, said inertia part being slidablyguided in said bore.

4. An impact fuze according to claim 1 wherein said inertia part is madeof a material of a density greater than that of the material of whichsaid firing pin is made.

References Cited by the Examiner UNITED STATES PATENTS 2,167,197 7/1939Brandt 102-79 2,871,788 2/1959 Guerne 10271 2,945,440 7/1960 Vogt 10216BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner.

1. AN IMPACT FUZE FOR A SPINNING PROPECTILE WHICH COMPRISES, INCOMBINATION, A FUZE CASE FIXED WITH RESPECT TO SAID PROPECTILE ANDHAVING A LONGITUDINAL AXIS OF ROTATION, A FIRING PIN SLIDABLELONGITUDINALLY IN SAID CASE IN THE DIRECTION CORRESPONDING TO FIRING INRESPONSE TO THE STOPPING OF SAID PROJECTILE BY AN OBSTACLE, SPRING MEANSIN SAID FUZE CASE OPERATIVELY CONNECTED WITH SAID FIRING PIN FOR URGINGIT LONGITUDINALLY WITH RESPECT TO SAID CASE IN SAID DIRECTION LOCKINGMEANS FOR YIELDINGLY PREVENTING SAID FIRING PIN FROM MOVING IN SAIDDIRECTION AS LONG AS THE SPEED OF REVOLUTION OF SAID PROJECTILE IS ABOVEA GIVEN VALUE, SAID LOCKING MEANS COMPRISING, ON THE ONE HAND, A SURFACEOF SAID FUZE CASE FOR REVOLUTION ABOUT SAID AXIS, SAID SURFACE HAVINGGENERATRICES OBLIQUE TO SAID AXIS AND CONVERGING IN SAID DIRECTION, AND,ON THE OTHER HAND, ADAPTED TO COOPERATE WITH SAID SURFACE BY SLIDINGENGAGEMENT THEREWITH, ROUNDED CENTRIFUGAL MEMBERS GUIDED IN SAID FIRINGPIN RADICALLY AND TRANSVERSELY TO SAID AXIS, WHEREBY AN INWARD MOVEMENTOF SAID CENTRIFUGAL MEMBERS TOWARD THE AXIS OF SAID FUZE CASE TAKESPLACE WHEN THE SPEED OF REVOLUTION OF SAID FUZE CASE ABOUT SAID AXISDROPS BELOW SAID GIVEN VALUE, AND AN INERTIA PART SLIDABLELONGITUDINALLY IN SAID FIRING PIN AND HAVING A SURFACE THEREOF, OFREVOLUTION ABOUT SAID AXIS AND CONVERGING IN THE SAME DIRECTION AS SAIDFIRST MENTIONED SURFACE, IN ENGAGEMENT WITH SAID CENTRIFUGAL MEMBERS,WHEREBY SAID INERTIA PART IS PUSHED LONGITUDINALLY IN A DIRECTIONOPPOSED TO THE FIRST MENTIONED DIRECTION WITH RESPECT TO SAID FUZE CASEIN RESPONSE TO A MOVEMENT OF SAID CENTRIFUGAL MEMBERS TOWARD SAID AXIS.